1. Field of the Invention
The present invention relates to a semiconductor integrated circuit, and more particularly, to a semiconductor integrated circuit using a direct-coupled field effect transistor logic (DCFL) configuration for low power consumption.
2. Description of the Related Art
Recently, gallium arsenide semiconductor integrated circuits (GaAs ICs), because of their low power consumption and high-speed operating capability, have been finding wide practical application, with good results, in areas where a high-speed interface is required.
At the present state of the art, GaAs ICs are seldom used by themselves in systems, etc., but are usually combined with CMOS or other silicon ICs with GaAs ICs used only in areas where high-speed operation is required. In such cases, the system's supply voltage is set to match the operating voltage of the silicon IC, for example, 3.3V or 5.0V. That is, GaAs ICs, theoretically capable of operating with a supply voltage of 1V or less, have been used without making full use of their advantage of low power consumption.
In order to exploit the advantage of the low power consumption of GaAs ICs, a technique of vertical circuit stacking has been proposed in the prior art. This vertical circuit stacking technique involves using, for example, a current regulating circuit and reduces power consumption by reducing the bias applied to each circuit block to a fraction of the supply voltage, as compared to a configuration where circuit blocks are simply connected in parallel between two power supplies (a high voltage supply line and a low voltage supply line).
The prior art vertical circuit stacking technique requires inserting the current regulating circuit as an additional circuit between the high voltage and low voltage supply lines, but this has led to the problems that the power consumption of this current regulating circuit becomes large, and that the provision of the current regulating circuit increases the circuit area.
A prior art semiconductor circuit and its associated problems will be described in detail later with reference to a drawing.